/* 全局样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: "Microsoft Yahei", sans-serif;
    background-color: #fff;
    color: #333;
}

a {
    text-decoration: none;
    color: #333;
}

ul {
    list-style: none;
}

/* 顶部导航栏样式 */
.top-nav {
    background-color: #0f2e4e;
    padding: 10px 0;
}

.top-nav ul {
    display: flex;
    justify-content: flex-start;
    align-items: center;
}

.top-nav ul li {
    margin: 0 15px;
}

.top-nav ul li a {
    color: #fff;
}

.top-nav .right-nav {
    margin-left: auto;
}

/* 二级导航栏样式 */
.sub-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 20px;
    border-bottom: 1px solid #eee;
}

.sub-nav-left .logo {
    color: #0f2e4e;
    font-size: 24px;
    font-weight: bold;
    margin-right: 20px;
}

.sub-nav-left a {
    margin-right: 15px;
}

.icon-btn {
    background: none;
    border: none;
    cursor: pointer;
    margin-left: 10px;
}

.icon-btn img {
    width: 20px;
    height: 20px;
}

/* 横幅样式 */
.banner img {
    width: 100%;
    height: 300px;
    object-fit: cover;
}

/* 最热视频部分样式 */
.hot-videos {
    padding: 30px;
}

.hot-videos h2 {
    text-align: center;
    margin-bottom: 20px;
    font-weight: normal;
}

.video-grid {
    display: flex;
}

.large-video {
    width: 60%;
    height: 250px;
    object-fit: cover;
    margin-right: 20px;
}

.small-videos {
    display: flex;
    flex-direction: column;
    width: 40%;
}

.small-videos img {
    width: 100%;
    height: calc(250px / 3);
    object-fit: cover;
    margin-bottom: 10px;
}

.small-videos img:last-child {
    margin-bottom: 0;
}

/* 大咖推荐部分样式 */
.expert-recommend {
    padding: 0 30px 30px;
}

.expert-recommend h2 {
    text-align: center;
    margin-bottom: 20px;
    font-weight: normal;
}

.recommend-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
}

.recommend-grid img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

/* 底部样式 */
.footer {
    background-color: #0f2e4e;
    color: #fff;
    text-align: center;
    padding: 20px 0;
}

.top-btn {
    display: inline-block;
    background-color: #333;
    color: #fff;
    width: 30px;
    height: 30px;
    line-height: 30px;
    text-align: center;
    border-radius: 50%;
    margin-bottom: 10px;
}